Boiler Replacement Cost UK – 2026 Price Guide

A mid-range 30kW combi boiler (Worcester Bosch Greenstar, Vaillant ecoTEC or Ideal Logic Max) costs £2,000–£3,200 fully installed in a like-for-like swap on a 3-bed home in 2026. Budget brands (Baxi, Alpha, Glow-worm) run £1,800–£2,500; premium brands (Viessmann Vitodens) £3,000–£4,500. Add £400–£1,200 if you're relocating the boiler or upgrading pipework.

Combi boilers are best for small-to-medium homes (1-2 bathrooms) — cheapest to install, no tanks, instant hot water. System boilers suit larger homes (2-3 bathrooms) where multiple taps/showers run at once — they use a hot water cylinder for better flow. Regular (conventional) boilers are usually retained in period properties with existing cylinders and cold water tanks. The right answer depends on your home size, bathrooms, water pressure and existing system.

In 2026, the £7,500 Boiler Upgrade Scheme (BUS) grant makes an air source heat pump £8,000–£14,000 installed — roughly £500–£6,500 net after the grant for a typical install. Heat pumps work best in well-insulated homes with larger radiators or underfloor heating. Running costs are typically 30–50% lower than gas at 2026 electricity prices. If you're committed to decarbonising, a heat pump is often the better long-term choice.

Not always — but most manufacturers (Worcester Bosch, Vaillant, Ideal) require proof of flushing to validate warranty. A chemical flush (£80-£200) is sufficient for most installs; a full powerflush (£400-£700) is needed if your system is sludgy, has cold radiators, or has visible corrosion. Ask your engineer to assess — many include a chemical flush as standard and only upsell powerflush if needed.

A straightforward like-for-like combi swap typically takes 1 day (6-9 hours on-site). Changing boiler type (e.g. regular to combi) or relocating adds 1-3 days. System boiler installs with a new cylinder typically take 2 days. Heat pump installs take 2-5 days depending on radiator sizing and outdoor unit positioning.

Variance comes from: brand and model (Worcester Bosch vs Baxi), kW output (24kW vs 30kW vs 35kW), warranty length (7 vs 10 vs 12 years), whether a magnetic filter is fitted, whether a smart thermostat is included, flush type, and whether the installer is on the manufacturer's approved list (which extends warranties by 2-3 years at no cost). Cheap quotes often use a smaller boiler, shorter warranty, budget thermostat or skip the filter.

Yes. The UK government's plan to ban new gas boilers in new-build homes from 2025 has been delayed; there's currently no confirmed ban date for replacement boilers in existing homes. You can install a new gas boiler in 2026 without restriction. That said, trends are clear — BUS grants and energy prices increasingly favour heat pumps. If your current boiler has 2-5 years left, it may be worth waiting for heat pump prices to fall further; if it's failing now, a new gas boiler is a sensible bridge for the next 10-15 years.